Early initiation of sexual intercourse in adolescence has been shown to be a risk factor for teenage pregnancy and sexually transmitted diseases. The goal of this proposed project is to identify the influences of genetic and environmental factors and their interactions on risky sexual behavior in adolescence using a sub-sample of about 2,600 participants of the National Longitudinal Study of Adolescent Health (Add Health). This sub-sample includes measures of adolescent sexual behavior from Waves l-lll (1994-5, 1995-6, and 2002, respectively), DNA data from Wave III, and extensive measures of religious beliefs and practice as well as other social and demographic context. Our Aim 1 will test the main effects of genetic variants and religiosity on age at first sexual intercourse using the candidate gene variants already genotyped in the sibling sub-sample. These analyses will consider polymorphisms in SLC6A3, DRD4, DRD2, SLC6A4, & MAOA as well as measures of religiosity and other social and demographic context including family structure, parental education, occupation, income, and community-level characteristics. Our Aim 2 will test the hypothesis that the effects of genetic variants on age at first sexual intercourse, if they exist, depend on individual's religiosity. We will test the interactive effects between the polymorphisms in SLC6A3, DRD4, DRD2, SLC6A4, & MAOA and religiosity as well as other SES measures. All of these genes have been previously implicated in risky behaviors and have been hypothesized to be associated with the propensities for a variety of compulsive, impulsive, and addictive behaviors including ADHD, substance abuse, alcoholism, smoking, and binge eating. Previous work and our own preliminary work suggest that early initiation of sex is likely to be associated with these genetic variants. Add Health is a pioneer research program that deliberately integrates traditional social sciences with bio- genetic perspectives. Its prospective, longitudinal design, the large range of social, demographic, psychological, & behavioral measures, and the DNA sample will allow for an unprecedented investigation of how environmental factors interact with specific genetic polymorphisms to influence risky sexual behavior among adolescents.